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Multiprocessor computers have been around for quite a while, but dual-core
processors are a relatively new offering. Both Intel and AMD dual-core
processors are showing up in consumer-level servers, desktop systems, and
laptops. A dual-core processor is essentially a single CPU chip that’s
actually two processors. Since it’s really a single plug-in chip, though,
you see only a single CPU chip plugged in when looking at the motherboard.

If you’re using a Windows 2000, XP Professional, or Windows Server
operating system, you can open the Performance tab in Windows Task Manager (as
shown in Figure 1) to see that multiple processors are recognized by the
operating systems. Notice that the CPU Usage History has two windows; each
window represents a processor (CPU).

NOTE

To open the Windows Task Manager, press Ctrl+Alt+Del and then click the Task
Manager button, or right-click the Windows toolbar and select Task Manager. Then
click the Performance tab to see the CPU Usage History.

Setting Process Priority

Whether you have multiple physical processors or dual-core processors, the
operating system treats them as separate processors. Multitasking operating
systems receive processing requests from applications. These requests are known
as threads. The applications run as processes and the operating system
schedules those processes. You can see the running processes by clicking the
Processes tab. You can affect how applications run by making changes to the
processes listed there. The adjustments that you can make include changing the
base priority at which a process spawns threads, as well as setting the
processor affinity of the process. Both types of adjustments affect application
performance.

The Windows 32-bit operating systems schedule threads using 32 priority
levels, numbered from 0 to 31. The highest-numbered thread is processed first.
As threads wait to be processed, their priority levels are increased. The base
application priority determines the priority level at which threads begin. As a
Windows administrator, you can adjust the base priority of a process to a
variety of settings. The following table shows the priority levels for each of
these definable settings.

Setting

Priority Level

Realtime

24

High

13

AboveNormal

9

Normal

8

BelowNormal

7

Low

4

NOTE

Code developers have more scheduling options. See
Scheduling Priorities
on the Microsoft MSDN web site for more information.

If you right-click a process on the Task Manager’s Processes tab and
select Set Priority, you’ll see all six priority options. You can set the
Realtime priority only when you’re logged onto a system with
administrative rights.

WARNING

Be careful when using the Realtime setting. Many people (including me) have
caused their systems to stop responding by setting an application’s base
priority to Realtime.

When might you want to change the priority of a running process? If you have
a an application that you expect to run for a long time, but you want to
minimize the impact of that application on the computer’s performance
while you’re using it, you can set the less important process to run at a
BelowNormal or Low priority level. Conversely, if you have a critical
application that you want to receive processing time over all other applications
on the system, you can set the priority level to AboveNormal or High.

If you want a particular Windows application to always start with a base
priority other than normal, you can use the Start command in a batch file to
always launch that application at a higher priority. For example, if you wanted
to run an application named PriorityOne at a high priority, you could create a
batch file using the start command:

start /high c:\priorityone.exe

This command could be used to start the application at a high priority.